Microwave oven having generator power supply

ABSTRACT

A microwave oven and a method of operating the same is provided herein. The method includes the steps of: sensing that a door of the microwave is in an open state; interrupting a power input to a generator power supply unit comprising a first converter, a first energy reserve, a second energy reserve located downstream from the first energy reserve, and a second converter located between the first and second energy reserves; detecting an input voltage; and disabling the second converter if the detected input voltage is less than a threshold voltage that is proportional to the detected input voltage, wherein disabling the second converter triggers the second energy reserve to discharge, and wherein the time necessary to discharge the second energy reserve is free of influence from the first energy reserve and is independent of the detected input voltage.

BACKGROUND

The present disclosure generally relates to a cooking apparatus, andmore particularly, to a microwave oven having a generator power supplyunit with a discharge function.

A conventional microwave oven cooks food by a process of dielectricheating in which a high-frequency alternating electromagnetic field isdistributed throughout an enclosed cavity. A sub-band of the radiofrequency spectrum, microwave frequencies at or around 2.45 GHz causedielectric heating primarily by absorption of energy in water.

To generate microwave frequency radiation in a conventional microwave, avoltage applied to a high-voltage transformer results in a high-voltagepower that is applied to a magnetron that generates microwave frequencyradiation. The microwaves are then transmitted to an enclosed cavitycontaining the food through a waveguide. Cooking food in an enclosedcavity with a single, non-coherent source like a magnetron can result innon-uniform heating of the food. To more evenly heat food, microwaveovens include, among other things, mechanical solutions such as amicrowave stirrer and a turntable for rotating the food. A commonmagnetron-based microwave source is not narrowband and not tunable (i.e.emits microwaves at a frequency that is changing over time and notselectable). As an alternative to such a common magnetron-basedmicrowave source, solid-state sources can be included in microwave ovenswhich are tunable and coherent.

SUMMARY

According to one aspect of the present disclosure, a microwave oven isprovided having a door movable between an open state and a closed stateand a microwave generator for generating microwaves. A generator powersupply unit is provided having the following components ordered fromupstream to downstream: a first converter for converting a power inputto a power output; a first energy reserve electrically coupled to thefirst converter for receiving the power output; a second converterelectrically coupled to the first energy reserve for converting thepower output to a low voltage power output; and a second energy reserveelectrically coupled to the second converter for receiving the lowvoltage power output and supplying the low voltage power output to themicrowave generator. A detection circuit is configured to detect aninput voltage and disable the second converter based on the door beingin the open state, wherein disabling the second converter triggers thesecond energy reserve to discharge, and wherein the time necessary todischarge the second energy reserve is free of influence from the firstenergy reserve.

According to another aspect of the present disclosure, a microwave ovenis provided and includes a door movable between an open state and aclosed state and a microwave generator for generating microwaves. Agenerator power supply unit is provided having the following componentsordered from upstream to downstream: a first converter for converting apower input to a power output; a first energy reserve electricallycoupled to the first converter for receiving the power output; a secondconverter electrically coupled to the first energy reserve forconverting the power output to a low voltage power output; and a secondenergy reserve located downstream from the first energy reserve andelectrically coupled to the second converter for receiving the lowvoltage power output and supplying the low voltage power output to themicrowave generator. A detection circuit is configured to detect aninput voltage and disable the second converter based on the door beingin the open state, wherein disabling the second converter triggers thesecond energy reserve to discharge, and wherein the time necessary todischarge the second energy reserve is independent of the detected inputvoltage.

According to yet another aspect of the present disclosure, a method ofoperating a microwave oven to reduce microwave leakage is provided. Themethod includes the steps of: sensing that a door of the microwave is inan open state; interrupting a power input to a generator power supplyunit comprising a first converter, a first energy reserve, a secondenergy reserve located downstream from the first energy reserve, and asecond converter located between the first and second energy reserves;detecting an input voltage; and disabling the second converter if thedetected input voltage is less than a threshold voltage that isproportional to the detected input voltage, wherein disabling the secondconverter triggers the second energy reserve to discharge, and whereinthe time necessary to discharge the second energy reserve is free ofinfluence from the first energy reserve and is independent of thedetected input voltage.

These and other aspects, objects, and features of the present disclosurewill be understood and appreciated by those skilled in the art uponstudying the following specification, claims, and appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic view of a microwave oven according to oneembodiment;

FIG. 2 is a schematic view of an electrical connection between a powersource, a generator power supply unit, and an RF generator of themicrowave oven;

FIG. 3 is a graphical representation of a detection time for a maximuminput voltage provided to the generator power supply unit;

FIG. 4 is a graphical representation of a detection time for a minimuminput voltage provided to the generator power supply unit; and

FIG. 5 is a flow diagram of a method of operating the microwave oven toreduce microwave leakage.

DETAILED DESCRIPTION

It is to be understood that the specific devices and processesillustrated in the attached drawings, and described in the followingspecification are simply exemplary embodiments of the inventive conceptsdefined in the appended claims. Hence, other physical characteristicsrelating to the embodiments disclosed herein are not to be considered aslimiting, unless the claims expressly state otherwise.

As used herein, the term “and/or,” when used in a list of two or moreitems, means that any one of the listed items can be employed by itself,or any combination of two or more of the listed items can be employed.For example, if a composition is described as containing components A,B, and/or C, the composition can contain A alone; B alone; C alone; Aand B in combination; A and C in combination; B and C in combination; orA, B, and C in combination.

The present disclosure may be implemented in any environment using aradio frequency (RF) generator or amplifier capable of generating afield of electromagnetic radiation (e-field) in the radio frequencyspectrum regardless of the application of the e-field and regardless ofthe frequency or frequency range of the e-field. For purposes of thisdescription, any e-field generating device, for example, a microwavegenerator or infrared signal generator, will be generally referred to asan RF generator, or similar language, and any e-field applying device,such as a waveguide, an antenna, or anode/cathode coupling or pair, willbe generally referred to as an RF applicator. These descriptions aremeant to make clear that one or more frequencies or frequency ranges ofe-field may be included in the embodiments described herein. While thisdescription is primarily directed toward a microwave oven providing ane-field capable of heating and or cooking food (collectively,“cooking”), it is also applicable to alternative uses of e-fieldgeneration such as drying fabrics, for example.

FIG. 1 schematically illustrates an RF device in the form of a microwaveoven 10 including a cabinet 12 defining a cavity 14 forelectromagnetically heating and/or cooking food, or foodstuff, in thecavity 14. The microwave oven 10 also includes a door 16 movably mountedto the cabinet 12, an RF shielding layer, for example, wire mesh 18,removably or fixedly attached to the cabinet 12 and the door 16. Thedoor 16 is movable between an opened state and a closed state toselectively provide access to the cavity 14, for instance, to allow forinserting food items to be cooked or for removing food items previouslycooked. When closed, the door 16 and corresponding segment of the wiremesh 18 are configured to align with the cabinet 12 to effectivelyprevent access to, and/or effectively seal, the cavity 14. The cavity 14is further sealed due to the configuration of the wire mesh 18, whichoperates to prevent e-field leakage into, or out of, the cabinet 12 andcavity 14.

The microwave oven 10 further includes a microwave generator shown as anRF generator 24 having at least one RF amplifier, shown as a first solidstate RF amplifier 26 and a second solid state RF amplifier 28. Themicrowave oven 10 further includes at least one RF applicator, shown asa first RF applicator 30 and a second RF applicator 32, each of which isconfigured to apply an e-field 34 to the cavity 14. The microwave oven10 also includes a generator power supply unit 36, an interruptioncircuit 37, a power source 38 (e.g., mains power), and a controller 40.While the cavity 14 is shown to include the RF generator 24 and thefirst and second RF applicators 30, 32 located in opposing corners ofthe cavity 14, other embodiments contemplate alternative placements ofthe RF generator 24 and the first and second RF applicators 30, 32,including a configuration where the RF generator 24 and the first andsecond RF applicators 30, 32 are located outside of the cavity 14. Inone specific embodiment, the first and second RF applicators 30, 32 arewaveguides that feed an e-field into the cavity 14. Furthermore, whilethe generator power supply unit 36, interruption circuit 37, powersource 38, and controller 40 are generally shown outside of the cabinet12, they are collectively contemplated to be included as components ofthe oven 10, and various placements of the aforementioned components arecontemplated, which may include placement within the cavity 14, cabinet12, and/or wire mesh 18.

As shown, the first solid state RF amplifier 26 may be electricallycoupled with the first RF applicator 30 and the second solid state RFamplifier 28 may be electrically coupled with the second RF applicator32. The RF generator 24 may also be electrically coupled with thegenerator power supply unit 36, which may further be electricallycoupled to the power source 38 via the interruption circuit 37. Theinterruption circuit 37 is configured to electrically couple the powersource 38 to the generator power supply unit 36 when the door 16 is in aclosed state and electrically decouple the power source 38 to thegenerator power supply unit 36 when the door 16 is in an open state.Accordingly, the interruption circuit 37 may be electrically coupled toa door switch, shown as door switch 41, which is configured to provide asignal indicative of a state of the door 16 to the interruption circuit37. The controller 40 is shown communicatively coupled (illustrated asdotted lines) to the RF generator 24 and the generator power supply unit36. In operation, the controller 40 may provide communication signals toone or more of the foregoing components for controlling the operationthereof.

The RF generator 24 is configured to receive a power input from thegenerator power supply unit 36 and may generate one, two, three, four,or any number of RF signals, as needed by the particular ovenapplication. The RF generator 24 is further configured to deliver eachrespective signal to a corresponding RF amplifier 26, 28. In thedepicted embodiment, the RF generator 24 is capable of generating two RFsignals, each of which is delivered to the corresponding first andsecond solid state RF amplifiers 26, 28 such that each of the first andsecond solid state RF amplifiers 26, 28 amplifies an independent RFsignal. Thus, it is contemplated that each RF signal may correspond toat least one of the first and second RF amplifiers 26, 28. As anon-limiting example, it is contemplated that one RF signal maycorrespond to one RF amplifier, two RF signals may correspond to tworespective RF amplifiers, three RF signals may correspond to threerespective RF amplifiers, four RF signals may correspond to fourrespective RF amplifiers, and so on and so forth. In contrast, it isalso contemplated that one RF signal may correspond to, for example,two, three, or four RF amplifiers, such that each RF amplifier amplifiesthe same RF signal. Accordingly, it should be appreciated that anynumber of combinations and/or permutations of any number of RF signalsand/or RF amplifiers as described are contemplated.

Each of the first and second RF amplifiers 26, 28 may be correspondinglyconfigured to deliver the amplified signal to the one or more RFapplicators 30, 32, which are configured to direct the amplified RFsignal, shown as an e-field 34, into the cavity 14. The generator powersupply unit 36 may be additionally configured to operatively convertpower received from the power source 38 to an alternative power output.For example, the generator power supply unit 36 may be configured toconvert an alternating current (AC) power input to a high current, lowvoltage direct current (DC) power output. However, it should beappreciated that alternative power conversions are contemplated, and theexample provided is merely one non-limiting example of a powerconversion. Additionally, the controller 40 may be any appropriatedevice that is capable of receiving input signals, generating,processing, and/or determining commands, and providing the commandsand/or command signals based on said commands, as one or more outputs.For example, the controller 40 may include one or more programmablelogic devices, application specific integrated circuits, digital signalprocessors, and/or microcontrollers.

During operation of the microwave oven 10, food items to be cooked areplaced into the cavity 14 via the open door 16, and then the door 16 isclosed. The controller 40 operates to control the microwave oven 10 suchthat the power source 38 provides a power input to the generator powersupply unit 36, which is controlled to convert the power input from thepower source 38 to a sufficient power output delivered to the RFgenerator 24. One example of the generator power supply unit 36 mayinclude, for instance, converting an AC power input to a low voltage(DC) output. In response, the RF generator 24 may generate a radiofrequency electromagnetic radiation (e-field) signal, which may besignificantly or trivially amplified by each respective first and secondRF amplifier 26, 28, and delivered from each first and second RFamplifier 26, 28 to the respective first and second RF applicators 30,32 for application of the electromagnetic radiation to the cavity 14.

FIG. 2 schematically illustrates the power source 38, the interruptioncircuit 37, the generator power supply unit 36, and the RF generator 24in further detail. In the depicted embodiment, the generator powersupply unit 36 includes, as components, a bridge rectifier 44, at leastone converter shown as a first converter 46 and a second converter 48,and at least one energy reserve shown as a first energy reserve 50 and asecond energy reserve 52. For purposes of understanding, theaforementioned components are shown ordered in a linear arrangement tomore clearly illustrate the direction of power transfer, beginning atthe power source 38, then moving across the components from an upstreamto downstream direction (i.e., from left to right in FIG. 2 ), andultimately ending at the RF generator 24. As shown, the components ofthe generator power supply unit 36 are positioned on a voltage line 56and a ground line 58, both of which also serving to electrically connectthe power source 38, the generator power supply unit 36, and the RFgenerator 24. While a detection circuit 54 is illustrated as being acomponent of the generator power supply unit 36, it should beappreciated that the detection circuit 54 may be separately provided inother embodiments. With respect to any of the embodiments describedherein, operation of the detection circuit 54 may be based on a state ofthe door 16.

In the depicted embodiment, the interruption circuit 37 electricallycouples the power source 38 to the generator power supply unit 36 whilein a closed state, and electrically decouples the power source 38 to thegenerator supply 36 while in an open state. The power input provided bythe power source 38 to the generator power supply unit 36 may correspondto an AC power input. As shown, the interruption circuit 37 iselectrically connected to the bridge rectifier 44, which rectifies thepower input. In the depicted embodiment, the bridge rectifier achievesfull-wave rectification of the AC power input. The bridge rectifier 44is also electrically coupled to the first converter 46 for convertingthe power input to a power output. In the depicted embodiment, the firstconverter 46 is configured as an AC to DC converter so as to convert theAC power input to a DC power output. The first converter 46 iselectrically coupled to the first energy reserve 50, which receives thepower output, i.e., the DC power output, and may include a bulkcapacitor 60 that becomes energized from the DC power output suppliedthereto from the first converter 46. The second converter 48 iselectrically coupled to the first energy reserve 50 for converting theDC power output to a low voltage DC power output. The second energyreserve 52 is located downstream from the first energy reserve 50 and iselectrically coupled to the second converter 48 for receiving the lowvoltage DC power output and supplying the low voltage DC power output tothe RF generator 24.

In the depicted embodiment, the second converter 48 includes a first DCto DC converter 62 and a second DC converter 64, each configured toconvert the DC power output to the low voltage DC power output andindividually supply the low voltage DC power output to a correspondingone of a first output capacitor 66 and a second output capacitor 68 ofthe second energy reserve 52. In turn, the first and second outputcapacitors 66, 68 individually supply the low voltage DC power output toa corresponding one of the first solid state RF amplifier 26 and thesecond solid state RF amplifier 28. In embodiments having additional RFamplifiers, a corresponding number of DC to DC converters and outputcapacitors may be similarly configured for individual power delivery.

With continued reference to FIG. 2 , the detection circuit 54 isconfigured to detect an input voltage and disable the second converter48 based on the door 16 being in the open state. In the depictedembodiment, detection circuit 54 detects the input voltage upstream fromthe first converter 46. For example, the input voltage may correspond toa rectified peak AC input voltage detected between the output of thebridge rectifier 44 and the input of the first converter 46 at a firstpoint 70 on voltage line 56 and a second point 72 on ground line 58. Forpurposes of disclosure, the voltage line 56 and the ground line 58 willbe collectively referred to herein as “the main line”. As shown, thedetection circuit 54 includes a comparator 74 for comparing the detectedrectified peak AC input voltage to a threshold voltage that isproportional to the detected rectified peak AC input voltage. If thedetected rectified peak AC input voltage is greater than the thresholdvoltage, the detection circuit 54 functions on standby, or in otherwords, does not disable the second converter 48. Such a scenario mayoccur, for example, when the door 16 is in a closed state and themicrowave oven 10 is executing a cooking operation. In such an instance,the power source 38 is electrically coupled to the generator powersupply unit 36 via the interruption circuit 37. As a result, thedetected rectified peak AC input voltage is generally greater than thethreshold voltage.

In contrast, if the detected rectified peak AC input voltage is lessthan the threshold voltage, the detection circuit 54 bypasses the bridgerectifier 44, the first converter 46, and the first energy reserve 50and disables the second converter 48 (e.g., each of the first and secondDC to DC converters 62, 64) by transmitting a switch-off signal 76thereto. In one implementation, the foregoing threshold condition issatisfied shortly after the door 16 is opened while a cookingapplication is underway. More specifically, when the door 16 is opened,the interruption circuit 37 electrically decouples the power source 38from the generator power supply unit 36, thereby ceasing the supply ofpower input to the generator power supply unit 36 from the power source38. As a result, the detected rectified peak AC input voltage willsatisfy the threshold condition after a period of time, typically nomore than 10 milliseconds. In operation, disabling the second converter48 triggers the second energy reserve 52 (e.g., each of the first andsecond output capacitors 66, 68) to quickly discharge in an effort tominimize the amount of microwave leakage due to the door 16 being openedwhile a cooking process is underway. Advantageously, since the detectioncircuit 54 bypasses components located downstream of the secondconverter 48, the time necessary to discharge the second energy reserve52 is free of influence from said components, namely the first energyreserve 50 (e.g., bulk capacitor 60). In other words, in embodimentswhere the detection circuit 54 is not included, the time necessary todischarge the second energy reserve 52 would be dependent on the timenecessary to discharge the first energy reserve 50, thereby increasingthe amount of microwave leakage while the door 16 is opened. As an addedadvantage, the inclusion of the detection circuit 54 enables the firstenergy reserve 50 to remain charged while the discharging of the secondenergy reserve 52 is underway. With respect to the depicted embodiment,the threshold voltage may be maintained at a predetermined value greaterthan zero so as to avoid a deactivation of the switch-off signal 76.

Referring to FIGS. 3 and 4 , graphs are shown illustrating a detectiontime at which the threshold condition (i.e., the detected rectified peakAC input voltage is less than the threshold voltage) is satisfiedfollowing an electrical decoupling of the power source 38 and thegenerator power supply unit 36. In FIG. 3 , the top graph illustrates amaximum peak AC input voltage 78 of approximately 264 V_(rms) and thebottom graph illustrates a corresponding detected rectified peak ACinput voltage 80 and voltage threshold 82. In FIG. 4 , the top graphillustrates a minimum peak AC input voltage 84 of approximately 177V_(rms) and the bottom graph illustrates a corresponding detectedrectified peak AC input voltage 86 and voltage threshold 88. It shouldbe appreciated that the maximum and minimum peak AC input voltages areprovided as non-limiting examples and may correspond to other values, ifdesired. With reference to both FIGS. 3 and 4 , the power source 38 isdecoupled from the generator power supply unit 36 at time T₁, therebyceasing the supply of the maximum and minimum peak AC input voltages 78,84, respectively. At time T₂, the threshold condition is satisfied,thereby prompting the detection circuit 54 to transmit the switch-offsignal 76 to the second converter 48 in order to trigger the dischargeof the second energy reserve 52. As can be seen in FIGS. 3 and 4 , thedetection time, i.e., the time between T₁ and T₂, at which the thresholdcondition is satisfied is the same regardless of the input voltagesupplied by the power source 38. Accordingly, by extension, the timenecessary to discharge the second energy reserve 52 is independent ofthe input voltage (i.e., the voltage associated with the input powersupplied by the power source 38) and the detected input voltage (i.e.,the voltage detected on the main line).

Referring to FIG. 5 , a flow diagram is shown illustrating a method 90of operating a microwave oven during a door opening event. The method 90may be implemented using the microwave oven 10 and associated componentsdescribed previously with reference to FIGS. 1-4 . In describing themethod 90, it is assumed that a cooking process is underway and the door16 of the microwave oven 10 is initially in the closed state.Additionally, it is assumed a user later opens the door 16 prior to thecompletion of the cooking process. With these assumptions in mind, themethod includes, at step 94, interrupting a power input to the generatorpower supply unit 36, as set forth at step 94. As described herein, thismay be achieved by electrically decoupling the power source 38 from thegenerator power supply unit 36 via the interruption circuit 37 when thedoor 16 is moved to an open state. In turn, the detection circuit 54 isoperated to detect an input voltage at step 96. As described herein, thedetected voltage may correspond to a detected rectified peak AC inputvoltage. If the detected input voltage satisfies a threshold condition(decision block 98), the detection circuit 54 disables the secondconverter 48 at step 100 via the switch-off signal 76. Otherwise, thedetection circuit 54 continues to detect the input voltage until thethreshold condition is satisfied. As described herein, disabling thesecond converter 48 triggers the second energy reserve 52 to discharge.By virtue of the detection circuit 54 bypassing the first energy reserve50, the time necessary to discharge the second energy reserve 52 is freeof influence from the first energy reserve 50 and is independent of thedetected input voltage, thus minimizing the exposure to microwaveleakage. The second converter 48 may remain disabled until the door 16is returned to a closed state, at which point the switch-off signal isdeactivated, as set forth at step 102.

For purposes of this disclosure, the term “coupled” (in all of itsforms, couple, coupling, coupled, etc.) generally means the joining oftwo components (electrical or mechanical) directly or indirectly to oneanother. Such joining may be stationary in nature or movable in nature.Such joining may be achieved with the two components (electrical ormechanical) and any additional intermediate members being integrallyformed as a single unitary body with one another or with the twocomponents. Such joining may be permanent in nature or may be removableor releasable in nature unless otherwise stated.

It is also important to note that the construction and arrangement ofthe elements of the device as shown in the exemplary embodiments isillustrative only. Although only a few embodiments of the presentinnovations have been described in detail in this disclosure, thoseskilled in the art who review this disclosure will readily appreciatethat many modifications are possible (e.g., variations in sizes,dimensions, structures, shapes and proportions of the various elements,values of parameters, mounting arrangements, use of materials, colors,orientations, etc.) without materially departing from the novelteachings and advantages of the subject matter recited. For example,elements shown as integrally formed may be constructed of multiple partsor elements shown as multiple parts may be integrally formed, theoperation of the interfaces may be reversed or otherwise varied, thelength or width of the structures and/or members or connector or otherelements of the system may be varied, the nature or number of adjustmentpositions provided between the elements may be varied. It should benoted that the elements and/or assemblies of the system may beconstructed from any of a wide variety of materials that providesufficient strength or durability, in any of a wide variety of colors,textures, and combinations. Accordingly, all such modifications areintended to be included within the scope of the present innovations.Other substitutions, modifications, changes, and omissions may be madein the design, operating conditions, and arrangement of the desired andother exemplary embodiments without departing from the spirit of thepresent innovations.

It will be understood that any described processes or steps withindescribed processes may be combined with other disclosed processes orsteps to form structures within the scope of the present disclosure. Theexemplary structures and processes disclosed herein are for illustrativepurposes and are not to be construed as limiting.

It is also to be understood that variations and modifications can bemade on the aforementioned microwave oven 10 without departing from theconcepts provided herein, and further it is to be understood that suchconcepts are intended to be covered by the following claims unless theseclaims by their language expressly state otherwise.

The above description is considered that of the illustrated embodimentsonly. Modifications of the device will occur to those skilled in the artand to those who make or use the device. Therefore, it is understoodthat the embodiments shown in the drawings and described above is merelyfor illustrative purposes and not intended to limit the scope of thedevice, which is defined by the following claims as interpretedaccording to the principles of patent law, including the Doctrine ofEquivalents.

What is claimed is:
 1. A microwave oven comprising: a door movablebetween an open state and a closed state; a microwave generator forgenerating microwaves, the microwave generator including at least onesolid state amplifier; and a generator power supply unit comprising thefollowing components ordered from upstream to downstream: a firstconverter for converting a power input to a power output; a first energyreserve electrically coupled to the first converter for receiving thepower output; a second converter electrically coupled to the firstenergy reserve for converting the power output to a low voltage poweroutput; and a second energy reserve electrically coupled to the secondconverter for receiving the low voltage power output and supplying thelow voltage power output to the at least one solid state amplifier ofthe microwave generator; and a detection circuit configured to detect aninput voltage and disable the second converter when the input voltage isless than a threshold voltage as a result of the door being in the openstate, wherein disabling the second converter triggers the second energyreserve to discharge, and wherein the time necessary to discharge thesecond energy reserve is free of influence from the first energyreserve.
 2. The microwave oven as claimed in claim 1, further comprisingan interruption circuit for electrically decoupling the generator powersupply unit from a power source configured to supply the power input,and wherein the interruption circuit electrically decouples thegenerator power supply unit from the power source if the door is in theopen state.
 3. The microwave oven as claimed in claim 1, wherein thedetection circuit comprises a comparator for comparing the detectedinput voltage to the threshold voltage that is proportional to thedetected input voltage.
 4. The microwave oven as claimed in claim 3,wherein the detection circuit transmits a switch-off signal fordisabling the second converter if the detected input voltage is lessthan the threshold voltage.
 5. The microwave oven as claimed in claim 4,wherein the threshold voltage is maintained at a value greater thanzero.
 6. The microwave oven as claimed in claim 1, wherein the powerinput comprises an AC power input, the power output comprises a DC poweroutput, the low voltage power output comprises a low voltage DC poweroutput, and the input voltage comprises a rectified peak AC inputvoltage.
 7. The microwave oven as claimed in claim 1, wherein the inputvoltage is detected upstream of the first converter.
 8. The microwaveoven as claimed in claim 1, wherein the detection circuit bypassescomponents of the generator power supply unit located upstream from thesecond converter such that the first energy reserve remains chargedwhile the discharging of the second energy reserve is underway.